Variants Explained: Mutation, Variant, VOC

Variants of Concern (VOC) and Variants under Investigation (VUI)

In the video, you will hear from the Variant Hunters, part of a team of scientists working in the UK’s sequencing effort to combat COVID-19. But what are variants of a virus exactly? How are these named so we can make sense of them?

SARS-CoV-2 virus has genetically changed gradually over time from the original Wuhan-1 strain at beginning of the pandemic. This has led to multiple variants of the virus circulating globally. Some of these variants, based on the mutations in the genome, have been classified as VOCs and VUIs as they carry an increased risk to global public health. This could be in the form of increased transmissibility, increased virulence or decreased effectiveness of public health measures for VOCs. Variants are classified as VUIs if they carry predicted genetic changes that could increase transmissibility, severity or immune escape and have been shown to cause community transmission in multiple countries alongside increasing number of cases over time.

Classification of these variants and associated lineages are primarily done by three large working groups Pango, NextStrain and GISAID. The VOC/VUI nomenclature for variants is primarily used in the UK. The WHO classifies variants as VOC, Variants of Interest (VOI) and Variants under Monitoring (VUM). ECDC primarily follows the WHO classification but also has an additional category of De-escalated Variants. The CDC nomenclature includes Variant Being Monitored (VBM), VOI, VOC, and Variant of High Consequence (VOHC). You can find a list of the current VOI and VOC in step 2.15

Although some of the terms used in the classification overlap between these organisations, the list of variants defined within each group differs slightly between each organization. In the steps ahead you will see a table of VOC/VUI defined by UK Health Security Agency along with variants that are being monitored. Relevant classification from other organizations is also provided.

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